feat: complete OTEL tracing across all services with pipeline bridge and docs

Extends tracing to every remaining module: all 23 API route handlers,
correlation engine, sniffer (fingerprint/p0f/syslog), prober (jarm/hassh/tcpfp),
profiler behavioral analysis, logging subsystem, engine, and mutator.

Bridges the ingester→SSE trace gap by persisting trace_id/span_id columns on
the logs table and creating OTEL span links in the SSE endpoint. Adds log-trace
correlation via _TraceContextFilter injecting otel_trace_id into Python LogRecords.

Includes development/docs/TRACING.md with full span reference (76 spans),
pipeline propagation architecture, quick start guide, and troubleshooting.

decnet/sniffer/worker.py

@@ -110,6 +110,7 @@ def _sniff_loop(
         logger.info("sniffer: sniff loop ended")
 
 
+@_traced("sniffer.worker")
 async def sniffer_worker(log_file: str) -> None:
     """
     Async entry point — started as asyncio.create_task in the API lifespan.